Internal combustion engines, including diesel engines, gasoline engines, gaseous fuel-powered engines, and other engines known in the art exhaust a complex mixture of air pollutants. These air pollutants are composed of gaseous compounds including, among other things, the oxides of nitrogen (NOX). Due to increased awareness of the environment, exhaust emission standards have become more stringent, and the amount of NOX emitted to the atmosphere by an engine may be regulated depending on the type of engine, size of engine, and/or class of engine.
In order to comply with the regulation of NOX, some engine manufacturers have implemented a strategy called selective catalytic reduction (SCR). SCR is an exhaust treatment process where a reductant, most commonly urea ((NH2)2CO) or a water/urea solution, is selectively injected into the exhaust gas stream of an engine and adsorbed onto a downstream catalyst. The injected urea solution decomposes into ammonia (NH3), which reacts with NOX in the exhaust gas to form water (H2O) and diatomic nitrogen (N2).
In some applications, multiple catalysts may be required for greater emissions control requirements. However, having multiple catalysts can increase exhaust backpressure and require significant amounts of space within the engine's exhaust system. In addition, it may be difficult to evenly distribute the exhaust and reductant mixture efficiently to each catalyst to maintain efficient reduction of NOX. These problems may increase packaging difficulties of the exhaust system.
One attempt to improve packaging of an exhaust system with multiple SCR catalysts is described in U.S. Patent Application Publication No. 2011/0146253 (“the '253 publication”) of Isada et al. that was published on Jun. 23, 2011. In particular, the '253 publication describes an aftertreatment module for use with an engine. The aftertreatment module includes a plurality of inlets and a plurality of outlets. The aftertreatment module also includes a plurality of exhaust treatment devices, including one or more banks of oxidation catalysts, a reductant dosing arrangement, and one or more banks of SCR catalysts. Many of these components serve multiple functions to utilize space within the aftertreatment module. For example, the bank of SCR catalysts is utilized to treat exhaust and as a wall of a restricted passage that causes exhaust to be evenly distributed across all of the SCR catalysts.
While the aftertreatment module of the '253 publication may help to improve packaging for exhaust systems with multiple catalysts, it may be less than optimal. Specifically, the aftertreatment module of the '253 publication may include unnecessary aftertreatment devices for certain applications, which may increase the overall packaging size of the aftertreatment module. A more compact aftertreatment module may be desirable. In addition, it may also be desirable to have the SCR catalysts positioned at a specific angle with respect to an exhaust flow of the inlet.
The aftertreatment module of the present disclosure solves one or more of the problems set forth above and/or other problems with existing technologies.